Software-defined networking (SDN), which controls the entire behavior of a network with software, is attracting attention. A technology or protocol called OpenFlow (OF) (registered trademark) is known as a method that implements SDN.
On an OF network complying with the OF protocol, the Link Layer Discovery Protocol (LLDP) may be used to detect the topology of the OF network. LLDP, which is internationally standardized as IEEE802.1AB, is a protocol used to detect and manage a layer 2 (L2) connection.
For example, an open flow controller (OFC) transmits and receives signals to and from a plurality of OF switches forming an OF network to detect connection relationships among these OF switches. Detecting a connection relationship between OF switches may be translated into finding a link between these OF switches.
LLDP may be used for signals that detect connection relationships among OF switches. Signals complying with LLDP may be translated into LLDP messages, LLDP frames, LLDP packages, and the like.
Examples of related art are described in International Publication Pamphlet No. WO 2011/080870, Japanese Laid-open Patent Publication No. 2014-42328, and Japanese Laid-open Patent Publication No. 2014-27443.